Synthesis of Wildland Fire Emission Factors
Smoke from wildland fires is a rich and complex mixture of gases and aerosols. Over 200 gas compounds have been identified in biomass smoke and wildland fires are a significant source of carbonaceous aerosol, carbon monoxide, greenhouse gases (carbon dioxide, methane), and many volatile organic compounds. Understanding and predicting the impact of wildland fires on air quality, atmospheric composition, and climate requires accurate knowledge of the composition and quantity of the trace gases and aerosol released. Wildland fire emissions of a pollutant X is typically modeled as the product of area burned (A), fuel loading (FL), combustion completeness (CC), and a specific emission factor (EFX): EX = A × FL × CC × EFX. Emission factors specify the mass of a pollutant emitted per unit mass of biomass burned and they are critical inputs for wildland fire emission models.
Over the past decade, laboratory and field studies have made great progress in characterizing the chemical composition of wildland fire smoke and quantifying emission factors. The project reviewed and synthesized biomass fire emission data from over 40 published studies to create an updated, comprehensive database of emission factors. Emission factors for many species vary with the combustion efficiency, which itself varies with ecosystem and fire type (prescribed, wildfire). While knowledge of emission factors has increased substantially in recent years, significant gaps regarding emissions from western prescribed fires, wildfires, and residual smoldering combustion remained. Field measurements of emissions for these fires types were limited and it was necessary to combine laboratory and field measurement to estimate emission factors for many species.
The emission factor database has been used in a revision of the Wildland Fire Emission Inventory (WFEI). The updated WFEI is being used in several research projects including an assessment of fire emission inventory tools and an effort to improve emissions in CarbonTracker, a carbon cycle decision support system for policy makers, industry, and scientists. The emission factor database is also being integrated into the First Order Fire Effects Model (FOFEM), a prescribed burning tool for land managers.